Effect of polypropylene fibers on the uplift behavior of model footings embedded in sand

ABSTRACT: The kinematics of failure and the uplift response of plates embedded in sand and in fiber-reinforced sand layers at distinct embedment depths, when subjected to vertical pullout tests, are the main topics discussed in the present technical note. The uplift capacity of plates in sand backfill layers is increased by the insertion of 0.5% fibers in the backfilled material. The enhancement of the uplift capacity increases from about 70% for embedment depth/plate diameter ratio (H/D) equal to 1.0 to about 30% for H/D equal to 2.0, when compared with sand backfill at the same embedment. Distinct failure patterns were observed for plates embedded in sand and in fiber-reinforced sand backfills: intense radial cracking was observed for sand backfill, but only a few concentric fissures were seen for fiber-reinforced backfill, the former starting at tiny displacements and the latter appearing at large displacements. The fiber-reinforced sand layers demonstrated the ability to continue to increase strength with ongoing deformation, suggesting a very ductile material.